of global change—how global change may affect what humans value and how those effects, or the anticipation of them, may affect human behavior.
The human causes and consequences of global change raise questions for both natural and social science. On the causes side, important human actions include releasing CFCs, burning fossil fuels, and cutting tropical moist forests. Much remains to be learned about the effects of these actions on the global environment, with many puzzles for natural scientists to solve. We do not yet understand, for example, where all the carbon dioxide emissions go, or how large an area certain ecological communities need to remain viable. The principal issues for the social sciences center on the causes of the human actions that proximally cause global change. On the consequences side, natural scientists need to address such questions as the effects of ozone depletion on the incidence of certain types of cancer and the implications of global climate change for agricultural production. The key issues for social scientists center on human responses to actual or anticipated global changes. In addition, as Figure 2-2 shows, human responses to actual or anticipated global changes frequently trigger feedback processes that affect the anthropogenic sources of global change. For example, faced with the prospect of ozone depletion or global warming, humans may act to reduce or eliminate their consumption of CFCs or their use of fossil fuels or make changes in demographic patterns or institutional arrangements. Such possibilities also fall into the domain of social science. We address them in Chapter 4.
What can the social sciences contribute to understanding the human dimensions of global change during the next decade? We have approached this question in two distinct ways. One is to imagine answering queries from policy makers and natural scientists working on global change issues. The other is to identify broad conceptual and theoretical constructs from social science that could be brought to bear on the problem in an illuminating fashion.
Policy makers and natural scientists interested in global change are likely to ask: Why does the United States consume so much